Cap screw or bolt



m, 3934. c. E. 5. PLACE ET AL 1,966,044

CAP SCREW OR BOLT Filed June 17/1933 INVENTORS M W Q.

ATTORNEYS Patented July 10, 1934 CAP SCREW OR BOLT Charles E. S. Place, Jersey City, and Marshall Van Winkle, Jr., Leonia, N. J.

Application June 17, 1933, Serial No. 676,242 17 Claims. for. 151-32) This invention relates to an improvement in cap screws or bolts and has for its object to provide a cap screw or bolt which will be securely locked when tightened in the work and automatically held in suchposition without the use of lock washers or other similar devices.

Another object is to provide a self-locking cap screw or bolt which, when in action or use, will compensate for the contraction and expansion of the metals in contact therewith.

Another object is to provide a self-locking cap screw or bolt which is inexpensive to manufacture, reliable and efficient in operation.

Another object is to provide a self-locking cap screw or bolt, in which its efficiency and usability is limited only by the wearing of the screw threads on the shank.

Another object is to provide certain improvements in the form, construction and arrangement of the several parts whereby the above named and other objects may effectively be attained.

A practical embodiment of our invention is represented in the accompanying drawing, in which Fig. 1 represents a plan view of our improved cap screw applied to the work;

Fig. 2 represents a vertical central section;

Fig. 3 represents a horizontal section taken in the plane of the line IIIIII of Fig. 2, looking in the direction of the arrows;

' Fig. 4 represents a detail vertical section of a bolt having our improved headapplied thereto, and a nut in operation;

5 represents a, plan view of a modified form of recess in the cap screw or bolt; and 1;

Fig. 6 represents a vertical central section of the same.

In the form shown in Figs. 1 to 3 inclusive, we have shown the application of our improved cap screw to two plates denoted by 1, 2, of which the plate 1 has a hole 3 and the plate 2 a screw threaded hole 4. The cap screw comprises a shank 5 having screw threads 6 which pass through the hole 3 in the plate 1 into engagement with the screw threads 4 of the plate 2 and a head. 'l'which contacts with the plate 1. This head '7 has, in the present instance, a hexagonal periphery, but it may be square or any other desired form. The top of the head '7 is formed with a longitudinal central bore 8, preferably circular in cross section which extends downwardly into the head and has a bottom 9. The depth of this longitudinal central bore 8 is less than the thickness of the head. In the under side of the'head there is developed an annular channel 10, the inner peripheral Wall of which is formed by the shank 5. The width of this channel 10 is such as to provide an annular bearing or contacting surface 11 for the head. The area of this bearing surface 11 is preferably equal to the cross sec-' tional area of the shank 5, but in some instances, the area of the bearing surface may be equal to any cross sectional area between the area of the shank and the area at the root of the threads, but never less than the cross sectional area at the root of the threads, since the strength of the shank or resistance to the breaking point is governed by the cross sectional area at the root of the thread. The bottom 12 of the channel 10 is preferably disposed in a horizontal plane which is spaced from the bottom 9 of the longitudinal bore 8, so that the metal in the head between the bottom 9 of the bore 8 and the top of the channel 10 will form a relatively thin annular wall 13. diaphragm and is equal in strength to carry the maximum load vproducible in a bolt when fully This wall 13 is capable of functioning as a stressed. By reason of this construction, the

natural resilience in the metal is utilized and the wall flexed within the elastic limit.

In applying the cap screw to the work, the threaded end of the shank 5 is passed through the hole 3 of the plate 1 and brought into engagement with the threaded hole 4 in the plate 2, Where it is rotated until the annular bearing surface llabuts the plate 1, after which the tightening torque on thehead will cause a further movement of the surface 11 on the plate and the shank in the threaded hole, which movement between the bearing surface and shank is compensated for by the flexing of the metal forming the wall 13. This flexing action is accounted for by the fact that the stresses between the annular bearing surface 11 and the plate 1, and the threads on the shank and hole are disposed in the same longitudinal direction. The stresses between the bearing surface and plate and in the shank will vary in relation to the degree of flexing of the annular wall 13 which is relatively thin and permits of a slight resiliency between the shank and the surface, so that the screwing out torque between the threads of the cap screw and the threads of the work will be capable of keeping the cap screw locked against unintentional displacement. When the unscrewing torque is applied to the head of the cap screw the threads in the shank and in the hole release the longitudinal stress on the wall which, by its resiliency, will move upwardly and return to its normal or original form without leaving therein a permanent distortion or set. Thus, the cap screw may be utilized indefinitely or until the wear of its'threads limits its usefulness.

While we have shown and described a cap screw, it will be understood that similar results may be obtained from the form shown in Fig. 4, in which the bolt comprises a shank 14 having a threaded end 15 arranged to receive a nut 16 and a head 17. The head 1'7 is formed with a longitudinal central bore 18 provided with a bottom 19. An annular channel 20 is developed in the under side of the head leaving a peripheral bearing surface 21 for contacting with the work. In the application of this form, the shank of the bolt is passed through holes 22, 23, 24 in plates 25, 26, 27 respectively, until the bearing surface 21 contacts with the plate 25 and the nut 16 screwed against the plate 27. The tightening torque may be applied either to the head 17 or the nut 16, or both simultaneously, which in either instance will place the longitudinal stress on the wall 28 which in turn will flex and hold the nut from loosening on the bolt. With a bolt of this construction, temperature changes which cause the expansion and contraction of the metals in contact with the bolt will be automatically compensated for.

In the modification shown in Figs. 5 and 6,

the top of the head 29 of the cap screw or bolt is formed with an annular recess 30, which extends into the head a distance less than the thickness of the head and the walls of the recess are outwardly flared. The under side of the head has an annular channel 31 and a peripheral bearing surface 32. The metal in the head between the bottom of the annular recess 30 and the bottom of the channel 31 forms an annular wall 33.

It will be noted that in the forms shown in Figs. 2 and 4 the diameters of the cylindrical bores 8 and 18, respectively, are less than the diameters of the shanks 5 and 14, respectively; while in the form shown in Fig. 6 the outer major diameter of the annular recess 30 is less than the shank of the cap screw or bolt.

It is understood that various changes may be resorted to in the form, construction and arrangement of the several parts without departing from the spirit and scope of our invention; and hence, we do not intend to be limited to the details herein shown'and described except as they may be included in the claims.

. What we claim is:

1. A cap screw or bolt comprising, a screw threaded shank and a head, said head having its under face formed with a bearing surface spaced from the shank, and a centrally disposed longitudinal bore in its upper face terminating within the head.

2. A cap screw or bolt comprising, a screw threaded shank and a head, said head having its under face formed with an annular bearing surface spaced from the shank, and a centrally disposed longitudinal bore in its upper face terminating within the head.

3. A cap screw or bolt comprising, a screw threaded shank and a head, said head having its under face formed with an annular bearing surface spaced from the shank, the area of said annular bearing surface being substantially equal to the area of the cross sectional plane of the shank, and a centrally disposed longitudinal bore in its upper face.

4. A cap screw or bolt comprising, a screw threaded shank and a head, said head having its under face formed with an annular bearing surface spaced from the shank, the area of said annular bearing surface being substantially equal to the area at the pitch diameterof the screw threads on the shank,'and a centrally disposed longitudinal bore in its upper face.

5. A cap screw or bolt comprising, a screw threaded shank and a head, said head having its under face formed withan annularbcaring surface spaced from the shank, the area of said annular bearing surface being at least equal to the area at the root of the screw threads on the shank, and a centrally disposed longitudinal bore in its upper face.

6. A cap screw or bolt comprising, a screw threaded shank and a head, said head having in its under face an annular channel adiacent said shank and a peripheral bearing surface, and a centrally disposed longitudinal bore in its upper face terminating, within the head.

7. A cap screw or bolt comprising, a screw threaded shank and a head, said head having in its under face an annular channel adjacent said shank and an annular peripheral bearing surface, and a centrally disposed longitudinal bore in its upper face terminating within the head.

8. A cap screw or bolt comprising, a screw threaded shank and a head, said head having in its under face an annular channel adjacent said shank and an annular peripheral bearing surface, the area of said bearing surface being substantially equal to the area of the cross sectional plane of the shank, and a centrally disposed longitudinal bore in its upper face.

9. A cap screw or bolt comprising, a screw threaded shank and a head, said head having in its under face an annular channel adjacent said shank and an annular peripheral bearing surface, the area of said bearing surface being substantially equal to the area at the pitch diameter of the screw threads on the shank, and a centrally disposed longitudinal bore in its upper face.

10. A cap screw or bolt comprising, a screw threaded shank and a head, said head having in its under face an annular channel adjacent said shank and an annular peripheral bearing surface. the area of said bearing surface being at least equal to the area at the root of the screw threads on the shank, and a centrally disposed longitudinal bore in its upper face.

11. A cap screw or bolt comprising, a screw threaded shank and a head, said head having in its under face an annular channel adjacent said shank and a peripheral bearing surface, and a centrally disposed longitudinal bore in its upper face, the diameter of said bore being less than the diameter of the shank and the depth less than the thickness of the head.

12. A cap screw or bolt comprising, a screw threaded shank and a head, said head having in its under face an annular channel adjacent said shank and an annular peripheral bearing surface, and a centrally disposed longitudinal bore in its upper face, the diameter of said bore being less than the diameter of the shank and the depth less than the thickness of the head.

13. A can screw or bolt comprising, a screw threaded shank and a head, said head having in its under face an annular channel adjacent said shank and an annular peripheral bearing surface, the area of said bearing surface being substantially equal-to the area of the cross sectional plane of the shank, and a centrally disposed longitudinal bore in its upper face, the diameter of said bore being less than the diameter 01' the shank.

14. A cap screw or bolt comprising, a screw threaded shank and a head, said head having in its under face an annular channel adjacent said 7 shank and an annular peripheral bearing surface, the area of said bearing surface being substantially equal to the area at the pitch diameter of the screw threads on the shank, and a centrally disposed longitudinal bore in its upper face, the diameter of said bore being less than the diameter of the shank.

15. A cap screw or bolt comprising, a screw threaded shank and a head, said head having in its under face an annular channel adjacent said shank and an annular peripheral bearing surface, the area of said bearing surface being at least equal to the area at the root of the screw threads on the shank, and a centrally disposed longitudinal bore in its upper face, the diameter 16. A cap screw or bolt comprising, a screw threaded shank and a head, said head having its under face formed with a bearing surface spaced from the shank and a central longitudinally disposed annular recess in its upper face having a depth less than the thickness of the head.

17. A cap screw or bolt comprising, a screw threaded shank and a head, said head having its under face formed with a bearing surface spaced i'mm the shank and a central longitudinally disposed annular recess in its upper face, the outer major diameter of said annular recess being less than the diameter of the shank and having a depth less than the thickness of head.

CHARLES E. S. FLAQL'. MARSHALL VAN JH. 

